After #436 is merged, it would be nice if the theme also supported switching languages. The JSON file used for versions could naturally be extended to encode the info, e.g., each version entry could gain a new key like

"languages": {
    "en": "English",
    "fr": "français",
    "zh": "中文" 
}

to list which language(s) are available for that version of the docs (i.e., languages nested within versions). Alternatively the JSON could be restructured so that versions are nested within languages. Either way, the switcher dropdown will need to be adjusted to accommodate the new JSON structure and to display the version choices.